Integrated circuits are continually being built and interconnected in denser and more complex packages. These circuits are being used to address high technology electronic applications and often include circuits that are designed to operate at high frequencies and at relatively high power levels. For example, many high performance digital computers are being implemented using VLSI (very large scale integration) ECL (emitter coupled logic) circuits operating at frequencies approaching 400 mega-Hertz and power density levels approaching 30 Watts per square centimeter.
When used in a relatively dense package, this type of circuitry must meet rigidly defined electrical and mechanical specifications. These specifications concern line impedance continuity, adequate heat dissipation and minimal noise and cross-talk interference. Unfortunately, these design criteria have been met with only limited success in the prior art. For example, prior art structures which have been designed to interconnect components of high performance digital computers have included multiple layers consisting of conductors disposed in a polymer matrix. Those prior art structures have dielectric properties that allow high speed pulse propagation, but they are overly sensitive to thermal and/or mechanical stresses.
Other types of prior art structures have been designed to mitigate the sensitivities referred to above. For example, certain structures use cooling plungers attached to the top of the integrated circuit chips, while others use cooling plungers attached to the bottom of the chips. Each of these prior art structures, however, has been unable to provide high density circuits that adequately operate at high frequencies and with proper thermal relief.